Switronix PocketBase allows you to power the camera up to 5hrs with two Canon LP-E6 type batteries, while simultaneously charging the removable internal battery. We can see the first video overview from Cheesycam.
Though it is functional and probably the most affordable off-the-shelf power solution for the BMPC (currently), I can’t say that it has all it’s bells & whistles in place. The LP-E6 batteries don’t have an actual lock, which might be a concern when running around with a BMPC in hand. In order to get to your SD Card, you’ll need to get the camera off the PocketBase by first removing the left side battery to access the unusual thumb screw.
More information: Cheesycam.com